1. Field of the Invention
The present invention relates to a method and apparatus for allocating a multicast connection identifier (MCID) used for Internet protocol (IP) multicast packet transmission over a portable Internet network and transmitting the packet using the MCID, and more particularly, to a method of defining and allocating an MCID for IP version 6 (IPv6) multicast packet transmission over an IEEE 802. 16/Wireless Broadband (WiBro) network, and an IP multicast packet transmission process of a base station (BS) using the MCID. Namely, the present invention relates to a method and apparatus for allocating an extensible MCID over the IEEE 802.16/WiBro network in order to transmit an IPv6 multicast packet in a link layer using a connection ID (CID) that is used to transmit packets of an IP layer over a link layer.
2. Description of the Related Art
In general, a multicast is a transmission to specified users in which a user from among a group of users who are connected to a local area network (LAN) or Internet transmits information to several users and the several users who receive the information transmit the same information to many users in a bucket relay manner. Unlike a Unicast which is a transmission to a single specified user and a broadcast which is a transmission to many unspecified users, the multicast means a transmission of information to several specified terminals.
In order to transmit an IP multicast packet over a portable Internet network such as an IEEE 802.16 network, a base station (BS) which connects hosts according to characteristics of a point-to-multipoint connection in the portable Internet network is used.
In general, when a transmitting host transmits an IPv6 multicast packet in a link-local category to a BS1 over the IEEE 802.16 network, the BS1 transmits the received IP multicast packet to hosts in a subnet1 by using an MCID that is allocated to a destination address of the received IPv6 multicast packet. However, according to the related art, there is a problem in that it is difficult to transmit a multicast packet that is not in the link-local category but instead is in a site-local or global category over the IEEE 802.16 network. In addition, an MCID is generated for every IPv6 multicast address, so that there is a problem in terms of extensibility.
In particular, unlike a wireless network such as an IEEE 802.11, the IEEE 802.16/WiBro network does not support a multicast function in a link layer, so that it is difficult to use an IPv6 neighbor discovery function that is a basic necessity for applying the IPv6. Currently, a method of transmitting an IPv6 multicast packet by extending a CID in the IEEE 802.16/WiBro network is being discussed by the Internet Engineering Task Force (IETF).
Up until now, a method of transmitting an IPv6 link-local scope multicast packet has been discussed. In particular, the method includes allocating a CID to every IPv6 link-local scope multicast address. However, this method results in that too large a portion of a CID having a 16-bit length that is used publicly to transmit a unicast packet and a control packet in a link layer in addition to a multicast packet has to be used for the IPv6 multicast packet transmission. Therefore, transmission performance of the unicast packet or the like can be affected. In addition, when the number of multicast addresses increases, there is a problem in terms of extensibility.
Another method discussed together with the aforementioned method is a method of allocating a public CID for multicast packet transmission. In this method, there is a problem in that when multicast packets use the same CID, multicast packets in various categories cannot be transmitted over the same network.
In order to provide a IPv6 multicast service in a network, multicast packets having various scopes in addition to a link-local scope have to be transmitted at the same time.